Abstract

If you developed a super-sour candy, drink, or dessert, to whom would you sell it? Do people of all ages love sour, or is there a difference between the sour preferences of kids and adults?
In this mouth-puckering science project, you will find out by making batches of lemonade that vary in their sourness and have volunteers taste them!

Objective

Determine whether there is a difference between adults' and children's preferences for sour tastes.

APA Style

Science Buddies Staff.
(2014, August 5).
Do You Have the Willpower to Taste Something Sour?.
Retrieved March 31, 2015
from http://www.sciencebuddies.org/science-fair-projects/project_ideas/HumBio_p018.shtml

Share your story with Science Buddies!

Introduction

Do you know anyone who likes to eat lemons? Or loves really sour candies? Maybe you are one of those people! People have different definitions of what they find palatable (PAH-lih-tuh-bul), which means "good to eat." There are many different factors that go into deciding whether or not something is palatable. One of the biggest parts of that decision is how something tastes. Humans can sense five tastes: sour, salty, bitter, sweet, and umami (oo-MAH-mee), which is the non-salty part of how soy sauce tastes.

Taste is detected by the taste buds that line the tongue and other parts of the mouth. Figure 1 shows a diagram of a taste bud. Although there is some variation from person to person, the human tongue has an average of about 10,000 taste buds. Inside each taste bud are several receptor cells. These cells can sense the five different tastes, and they send that information to the brain.

Figure 1. Each taste bud contains many different taste receptor cells, which help to detect the five different tastes: sour, salty, bitter, sweet, and umami. (Adapted from Selbst Erstellt, 2008.)

In addition to taste, people think about several other factors when deciding if something is acceptable to eat. These include other components of flavor, like how spicy a food is or how it smells, the texture and temperature of a food, and whether the food is something they like eating for cultural or personal reasons. Figure 2 shows a diagram of the different factors people consider when making their food choices.

Figure 2. This diagram shows the different factors humans use to determine if a food is acceptable to eat or not. Taste, at the center of the diagram, is one of the most important factors; but other things, including what is typically considered "yummy" in a culture, are also part of the decision.

One job food scientists can have is working at companies to help them design new foods. One of the things they have to do is conduct sensory analysis, which is the scientific process of determining how people react to different foods, and then make decisions about whether or not they like them. Food scientists already know a lot about people's food preferences. For example, they know that babies usually prefer sweet foods, like applesauce and sweet potatoes, over more bitter foods, like broccoli. They also know that Americans and Europeans like mint-flavored toothpastes, while people in China and Japan prefer their toothpastes to be fruit-flavored. But what about sour? There are a lot of sour candies and drinks advertised on TV, in magazines, and in other places that tempt kids, but not many of those advertisements make the foods sound appealing to adults. Is there a difference in the percentage of kids versus adults who like sour-tasting foods?
In this human biology science project, you
can find out by conducting a taste test with four lemonades, each with a different concentration of citric acid. Citric acid is the natural chemical that gives citrus fruits, like limes, lemons, oranges, and grapefruit, their sour taste. Who do you think will like the sourest lemonade the best?

Terms and Concepts

Palatable

Umami

Taste bud

Receptor cell

Sensory analysis

Citric acid

Citrus fruits

Concentration

Stock solution

Questions

What are some foods that represent the five tastes that humans can detect?

What factors do people use to decide if they want to eat a certain food?

Are there any examples of adults and kids having different preferences for certain tastes?

News Feed on This Topic

,
,

Note: A computerized matching algorithm suggests the above articles. It's not as smart as you are, and it may occasionally give humorous, ridiculous, or even annoying results! Learn more about the News Feed

Materials and Equipment

Citric acid, 3 oz (85 grams), used for sprouting or canning foods; can be found as a powder or granules in some grocery stores. Check the spices, baking supplies, or health supplements aisles. Can also be ordered online from some vitamin companies, like LuckyVitamin.com and TheCatalog.com. Caution: only use food-grade citric acid.

Tablespoon measuring spoon

Measuring cups

Mixing spoon

Water

Containers that can hold and pour 1 liter of liquid, such as pitchers; thermoses; and empty, clean juice bottles (5)

Permanent marker

Masking tape

Citrus-flavored powdered drink mix, like lemonade flavor, enough to make 4 liters (which is the same as 4 quarts)

Refrigerator

Small paper cups (150)

Helper

Adult volunteers (15)

Kid volunteers between the ages of 5 and 11 years old (15)

Graph paper

Lab notebook

Disclaimer:
Science Buddies occasionally provides information (such as part numbers, supplier
names, and supplier weblinks) to assist our users
in locating specialty items for individual projects. The
information is provided solely as a convenience to our users. We do our best to make sure that part numbers
and descriptions are accurate when first listed. However, since part numbers do change as items are obsoleted
or improved, please send us an email if you run across any parts that are no longer available.
We also do our best to make sure that any listed supplier provides prompt, courteous service.
Science Buddies does participate in affiliate programs with
Amazon.com,
Carolina Biological,
and AquaPhoenix Education.
Proceeds from the affiliate programs help support Science Buddies, a 501( c ) 3 public charity. If you have any comments (positive or negative) related to
purchases you've made for science fair projects from recommendations on our site, please let us know. Write
to us at scibuddy@sciencebuddies.org.

Share your story with Science Buddies!

Experimental Procedure

Making the Lemonades

To conduct the tasting experiment, you will need to make four batches of lemonade or other citrus drink, each with a different concentration (amount) of citric acid. The more citric acid that is added to the drink, the more sour the liquid will taste.

The first step is to make a stock solution of the citric acid. A stock solution is a mixture that is more concentrated than any of the final mixtures. The stock solution can then be diluted to make all the other drinks. This is easier than measuring out the citric acid for each batch of lemonade because the amounts of citric acid would be too small and hard to measure by volume or weight for some of the less sour batches.

Using the measuring spoon, put 6 tablespoons (Tbsp) of your citric acid in one of your containers.

Add 3 cups of water to the pitcher and mix with a spoon until all the citric acid is dissolved.

This is your stock solution of citric acid. It has twice as much citric acid in it as the most sour batch of lemonade you will make.

Note: You can taste the stock solution if you want, it will not hurt you, but it will be very sour!

Using pieces of masking tape and a permanent marker, label each of the four remaining liquid containers with the numbers 1, 2, 3, and 4, which correspond to the information in the table below. Each container will hold a different batch of lemonade.

Following the directions on the package of the lemonade mix, add enough of the drink mix to each container to make 1 liter of the drink. Note: The instructions for the drink mix might list quantities in cups or quarts instead of in liters. 1 liter, 1 quart, and 4 cups are all the same amount of liquid.

Using the measuring cup and measuring spoon, add the citric acid stock solution and appropriate amount of water to each container. Table 1, below, shows how much of each ingredient should be added for each lemonade batch.

Lemonade Batch #

Level of Sourness

Quantity of Citric Acid Stock Solution to Add to the Drink Mix

Quantity of Water to Add to the Drink Mix

1

None

None

4 cups

2

Low; similar to 10% lemon juice

3 Tbsp

4 cups

3

Medium; similar to 50% lemon juice

2/3 cup

3 and 1/3 cups

4

High; similar to 100% lemon juice

2 cups and 2 Tbsp

2 cups

Table 1. Make your lemonade batches based on the recipes given here.

Use a spoon to mix each lemonade batch until all the drink mix is completely dissolved.

Refrigerate the lemonade batches until you are ready to have your volunteers taste-test them.

Conducting the Taste Test

You will need to gather all your volunteers at the same time.

With the permanent marker, label 30 paper cups for each lemonade batch.

In the end, you will have a total of 120 paper cups that will hold lemonade: 30 labeled #1, 30 labeled #2, 30 labeled #3, and 30 labeled #4.

On a large work surface, with plenty of space to set out all 120 cups, pour the lemonade batches into the appropriately labeled cups.

For example, batch #1 (the lemonade without any citric acid added to it) will go in the cups labeled #1.

You might want to have a helper move the cups out of the way for you as you pour them.

Try to keep each batch grouped closely together.

Pour plain water into 30 more cups—these cups do not have to be labeled with anything.

Give each volunteer one cup from lemonade batch #1.

Note: You can choose to have the volunteers taste the lemonades in any order you want, just make sure that each volunteer follows the same tasting pattern. However, passing them out in numerical order will probably help your volunteers remember which one they liked best and which they liked least.

Ask the volunteers to taste the first lemonade. Then pass each person a cup of water and have them take a sip to clear their palettes. Continue to pass out the lemonades, one at a time, asking the volunteers to taste them, and always having the volunteers take a sip of water in between tastings.

Once the volunteers have tasted all four batches of lemonade, ask them to tell you which was their favorite, and which was their least favorite. Record the results in a data table, like Table 2, below, in your lab notebook.

Volunteer #

Adult or Kid

Favorite Lemonade Batch #

Least Favorite Lemonade Batch #

1

2

3

Table 2. In your lab notebook, make a data table like this one to record your results in.

Analyzing the Data

Make a bar graph illustrating your data.

Make a bar graph showing how many of the volunteers chose each batch of lemonade as their favorite. You can either make two graphs, one for the adults and one for the kids, or one graph with different colored bars for the adult and kid data.

Using the same technique, make a bar graph showing how many of the volunteers chose each batch of lemonade as their least favorite.

You can make the graphs by hand or use a website like Create a Graph to make the graphs on the computer and print them.

Look at your graphs. Is there a difference between adults and kids for how many chose the sourest lemonade as their favorite? How about as their least favorite?

Share your story with Science Buddies!

Variations

Do kids and adults have different preferences for other tastes? Design experiments to test preferences for any or all of the other tastes: sweet, salty, bitter, and umami.

Does being a "picky" eater change how likely a person is to enjoy really sour foods? Ask your volunteers if they are picky, normal, or adventurous eaters. You'll need at least 10 people in each category. Then give them the sour taste test described above. Make bar graphs for each category of eater. Do you see any differences between the categories?

Ask an Expert

The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

Related Links

If you like this project, you might enjoy exploring these related careers:

Food Scientist or Technologist

There is a fraction of the world's population that doesn't have enough to eat or doesn't have access to food that is nutritionally rich. Food scientists or technologists work to find new sources of food that have the right nutrition levels and that are safe for human consumption. In fact, our nation's food supply depends on food scientists and technologists that test and develop foods that meet and exceed government food safety standards. If you are interested in combining biology, chemistry, and the knowledge that you are helping people, then a career as a food scientist or technologist could be a great choice for you!
Read more

Neurologist

Each time your heart beats, or you breathe, think, dream, smell, see, move, laugh, read, remember, write, or feel something, you are using your nervous system. The nervous system includes your brain, spinal cord, and a huge network of nerves that make electrical connections all over your body. Neurologists are the medical doctors who diagnose and treat problems with the nervous system. They work to restore health to an essential system in the body.
Read more

Biologist

Life is all around you in beauty, abundance, and complexity. Biologists are the scientists who study life in all its forms and try to understand fundamental life processes, and how life relates to its environment. They answer basic questions, like how do fireflies create light? Why do grunion fish lay their eggs based on the moon and tides? What genes control deafness? Why don't cancer cells die? How do plants respond to ultraviolet light? Beyond basic research, biologists might also apply their research and create new biotechnology. There are endless discoveries waiting to be found in the field of biology!
Read more

News Feed on This Topic

,
,

Note: A computerized matching algorithm suggests the above articles. It's not as smart as you are, and it may occasionally give humorous, ridiculous, or even annoying results! Learn more about the News Feed

Looking for more science fun?

Try one of our science activities for quick, anytime science explorations. The perfect thing to liven up a rainy day, school vacation, or moment of boredom.

Can you suggest any improvements or ideas?(Enter "no" if you have none.)

characters left

Overall, how would you rate the quality of this project?

Excellent
Very good
Good
OK
Poor

What is your enthusiasm for science after doing your project?

Very high
High
Moderate
Low
Very low

Compared to a typical science class, please tell us how much you learned doing this project.

Much more
More
About the same
Less
Much less

Optional:Attach a picture of your project (JPG, JPEG, GIF, PNG only)

Optional:Caption for picture

characters left

You can find this page online at: http://www.sciencebuddies.org/science-fair-projects/project_ideas/HumBio_p018.shtml

You may print and distribute up to 200 copies of this document annually, at no charge, for personal and classroom educational use. When printing this document, you may NOT modify it in any way. For any other use, please contact Science Buddies.